net/netfilter/nf_conntrack_snmp.c

   1 /*
   2  *      SNMP service broadcast connection tracking helper
   3  *
   4  *      (c) 2011 Jiri Olsa <jolsa@redhat.com>
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License
   8  *      as published by the Free Software Foundation; either version
   9  *      2 of the License, or (at your option) any later version.
  10  */
  11 #include <linux/kernel.h>
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/in.h>
  15
  16 #include <net/netfilter/nf_conntrack.h>
  17 #include <net/netfilter/nf_conntrack_helper.h>
  18 #include <net/netfilter/nf_conntrack_expect.h>
  19
  20 #define SNMP_PORT       161
  21
  22 MODULE_AUTHOR("Jiri Olsa <jolsa@redhat.com>");
  23 MODULE_DESCRIPTION("SNMP service broadcast connection tracking helper");
  24 MODULE_LICENSE("GPL");
  25 MODULE_ALIAS_NFCT_HELPER("snmp");
  26
  27 static unsigned int timeout __read_mostly = 30;
  28 module_param(timeout, uint, S_IRUSR);
  29 MODULE_PARM_DESC(timeout, "timeout for master connection/replies in seconds");
  30
  31 int (*nf_nat_snmp_hook)(struct sk_buff *skb,
  32                         unsigned int protoff,
  33                         struct nf_conn *ct,
  34                         enum ip_conntrack_info ctinfo);
  35 EXPORT_SYMBOL_GPL(nf_nat_snmp_hook);
  36
  37 static int snmp_conntrack_help(struct sk_buff *skb, unsigned int protoff,
  38                 struct nf_conn *ct, enum ip_conntrack_info ctinfo)
  39 {
  40         typeof(nf_nat_snmp_hook) nf_nat_snmp;
  41
  42         nf_conntrack_broadcast_help(skb, protoff, ct, ctinfo, timeout);
  43
  44         nf_nat_snmp = rcu_dereference(nf_nat_snmp_hook);
  45         if (nf_nat_snmp && ct->status & IPS_NAT_MASK)
  46                 return nf_nat_snmp(skb, protoff, ct, ctinfo);
  47
  48         return NF_ACCEPT;
  49 }
  50
  51 static struct nf_conntrack_expect_policy exp_policy = {
  52         .max_expected   = 1,
  53 };
  54
  55 static struct nf_conntrack_helper helper __read_mostly = {
  56         .name                   = "snmp",
  57         .tuple.src.l3num        = NFPROTO_IPV4,
  58         .tuple.src.u.udp.port   = cpu_to_be16(SNMP_PORT),
  59         .tuple.dst.protonum     = IPPROTO_UDP,
  60         .me                     = THIS_MODULE,
  61         .help                   = snmp_conntrack_help,
  62         .expect_policy          = &exp_policy,
  63 };
  64
  65 static int __init nf_conntrack_snmp_init(void)
  66 {
  67         exp_policy.timeout = timeout;
  68         return nf_conntrack_helper_register(&helper);
  69 }
  70
  71 static void __exit nf_conntrack_snmp_fini(void)
  72 {
  73         nf_conntrack_helper_unregister(&helper);
  74 }
  75
  76 module_init(nf_conntrack_snmp_init);
  77 module_exit(nf_conntrack_snmp_fini);